Add cron job to the provided machines

add_cron.sh

#! /bin/bash

# Usage: 
#   sh add_cron.sh [key_file] [user] ip

key_file=$1
username=$2
ip=$3

if [ $# -le 2 ]; then
  echo "Usage: sh add_cron.sh [key_file] [user] ip"
  exit 1;
fi

ssh -i "$key_file" "$username"@"$ip" "(crontab -l 2>/dev/null; echo '00 00 * * * docker container prune -f && docker image prune -f &> /var/log/cleanup.log') | crontab -"

Add a cron job to remove docker unused images and containers.